Eyewitness

Eyewitness is a 1970 British thriller film directed by John Hough and starring Mark Lester, Susan George and Lionel Jeffries. Its plot follows a young English boy who, while staying with his grandfather and adult sister in Malta, witnesses a political assassination, and is subsequently pursued by the killers—however, due to his habitual lying, those around him are hesitant to believe his claims. It is an adaptation of the novel by Mark Hebden, the pen name for John Harris, and bears similarity to Cornell Woolrich's novelette "The Boy Cried Murder", originally adapted for film as The Window.

Synopsis from Wikipedia, CC BY-SA 4.0. Everything below written here.

Poster © the film's rights holders.